Well, in the short term there are two immediate impacts we’ll see by software developers having deep access into Outlook PST storage format: (1) faster development of Outlook plugins such as Xobni, and (2) easier migration of mail data out of Outlook and into services such as Rackspace Email and Google Apps. This move by Microsoft will drastically reduce the time it takes to develop these products because developers no longer have to reverse engineer the Outlook storage format.

Longer term, Outlook could become an apps platform where we see all sorts of third-party apps being developed that add value to the core feature-set of Microsoft Outlook, similar to what you see with Facebook Apps today but on your desktop. However, in order for this to play out, Microsoft will need to do more than just open up the storage format. They will have to also redesign Outlook with apps in mind so that apps can be easily developed and can feel like an integrated part of Outlook. They’ll also need to launch some sort of an “app store” model for third parties to distribute their apps, such as what has worked so successfully for Apple’s iPhone apps.

Or this announcement could simply be part of a less-sexy initiative where Microsoft is releasing more of their proprietary specifications in order to make lawyers in the EU and elsewhere happy. We’ll see.

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I hope they follow through with opening this data format. With cloud hosting solutions like Rackspace Apps and a few others out there, it’s almost a deal killer when a client needs to migrate 10+ years worth of business data stored in email folders from Microsoft Outlook to a hosted / cloud solution for email…